Cashew nut shell liquid (CNSL) occurs as a reddish brown viscous liquid in the soft honeycomb structure of the shell of cashewnut, a plantation product obtained from the cashew nut tree, Anacardium Occidentale L. Native to Brazil the tree grows in the coastal area of Asia and Africa. Cashewnut attached to cashew apple is grey colored, kidney shaped and 2.5-4 cm long. The shell is about 0.3 cm thick, having a soft leathery outer skin and a thin hard inner skin. Between these skins is the honeycomb structure containing the phenolic material popularly called CNSL. Inside the shell is kernel wrapped in a thin brown skin known as the testa.
The nut thus consists of the kernel (20-25%) the shell liquid (20-25%) and the testa (2%) and the rest being the shell. CNSL extracted with low boiling petroleum ether, contain about 90% an anacardic acid and about 10% cardol. CNSL on distillation gives a pale yellow phenolic derivatives, which are a mixture of biodegradable saturated and unsaturated m-alkyl phenols, including cardanol. Catalytic hydrogenation of these phenols gives a waxy material pre dominantly rich in tetrahydroanacardol.
CNSL and its derivatives have been known for producing high temperature phenolic resins and friction elements, as exemplified in U.S. Pat. Nos. 4,395,498 and 5,218,038. Friction lining production from CNSL is also reported in U.S. Pat. No. 5,433,774. Like wise, it is also known to form different types of friction materials, mainly for use in brake lining system of automobiles and coating resins from CNSL.
However, the first application of CNSL in malting lubricating oil additives was disclosed by us in U.S. Pat. Nos. 5,916,850 and 5,910,468.
There is a continuing need to produce fuels that meet the ever-stricter requirements of the regulatory agencies around the world. Of particular need are fuels that have low levels of aromatics and sulfur. While regulated fuel properties are not identical for all regions, there are generally achieved by the use of hydroprocessing (hydrotreating) to lower levels of both aromatics and sulfur. Hydrotreating, particularly hydrodesulfurisation, is one of the fundamental process for refining and chemical industries. The removal of feed sulfur by conversion to hydrogen sulfide is typically achieved by reaction with hydrogen over non-noble metal sulfides, especially those of Co/Mo, Ni/Mo and Ni/W, at fairly rigorous temperatures and pressures to meet product quality specifications. Environmental considerations and mandates have driven product quality specifications in the direction of low sulfur and aromatics levels.
During hydrotreating, aromatics are saturated and feed sulfur is converted to hydrogen sulfide. While this achieves the desired result with respect to emissions, it has an adverse effect on the inherent lubricity properties of the distillate fuel. Equipment can be designed for low fuel lubricity but sufficient lubricity is required for existing equipment. This lower lubricity leads to increased maintenance cost of diesel engines e.g. pump failures, and in extreme cases to catastrophic failure of the engine.
A number of types of additives have already been proposed in order to solve this problem. Antiwear additives have thus been added to diesel fuels, some of these being known in the field of lubricant, of the type of fatty acid esters and of unsaturated fatty acid dimers, aliphatic amines, esters of fatty acids and of diethanolamine and long chain aliphatic monocarboxylic acids as described in U.S. Pat. Nos. 2,252,889, 4,185,594, 4,204,481, 4,208,190 and 4,428,182. Most of these additives exhibit a sufficient lubricating power, but in concentrations, which are much too, high, and this is economically highly disadvantageous for purchase. Moreover, additives containing acid dimers, like those containing acid trimers cannot be employed in fuels fed to vehicles in which fuel may come in contact with the lubricating oil because these acid forms, by chemical reaction, deposits, which are sometimes insoluble in the oil but, above all, incompatible with detergents are usually employed.
U.S. Pat. No. 4,609,376 recommends the use of antiwear additives obtained from esters of mono- and poly-carboxylic acids and polyhydroxylated alcohols in fuels containing alcohols in their composition. U.S. Pat. No. 2,686,713 recommends the introduction of tall oil up to 60 ppm in diesel fuels in order to prevent rust formation on metal surfaces in contact with these fuels.
Another chosen route is to introduce vegetable oil esters or vegetable oil themselves into these fuels to improve their lubricating power or their lubricity. These include esters derived from rapeseed, linseed, soya and sunflower oils themselves (EP 635,558, EP 605,857). One of the major disadvantages of these esters is their low lubricating power at a concentration lower than 0.5% by weight in the fuels.
To improve the lubricating power of diesel fuels, the WO 95/33805 recommends the introduction of cold resistance additives consisting of nitrogenous additives containing one or more >N—R13 groups in which R13 contains 12 to 24 carbon atoms, is linear, slightly branched or alicyclic and aromatic, it being possible for the nitrogenous group to be linked via CO or CO2 and form amine carboxylates or amides.
A suitable diesel fuel lubricity standard has been established by using the HFRR method (ISO 12156-1 standard): the HFRR wear scar diameters (WSD) obtained after testing a diesel fuel must be lower than 460 μm to ensure that this fuel has sufficient lubricity. When necessary, better lubricity can be restored easily by adding additives. However, these additives must have good physical and chemical stability alone or after incorporation in multifunctional formulation. They must also be fully compatible with other additives that may be present in the fuel such as flow improvers, wax antisettling additives, detergents etc.
To verify this physical and chemical compatibility and to ensure that each additive maintain its full efficiency after being mixed with others in multifunctional formulations or in fuel itself, no harm tests are carried out.
Publication JP-A-110001692 describes use of a specific mixture of C8-C30 fatty acid ester to improve the lubricity of low sulfur (0.2 wt %) middle distillate fuel oils, having an aromatic content of ≦40 wt %, suitable for use as diesel fuel. WO 99/00467 describes a fuel composition of improved lubricity comprising of lubricity additive which is an alkanolamide of an aryl-substituted fatty acid, the composition further necessarily comprises a haze inhibiting amount of dehazer.
The publication WO 01/88064 A2 describes a fuel composition, which exhibit improved antistatic properties comprising of liquid fuel which contains less than 500 ppm by weight sulfur, 0.001 to 1 ppm of hydrocarbyl monoamine or hydrocarbyl substituted poly (alkyleneamine) and 10 to 500 ppm of at least one fatty acid containing 8 to 24 carbon atoms or an ester thereof. Ikura et al in US Pat No. 2002/0178650 A1 describes a low temperature stable diesel fuel composition and a solubilizer of C14-18 fatty acid from biodegradable sources eg. tall oil or depitched tall oil.
A PCT WO 01/44415 patent describes use of heterocyclic group containing polycyclic aromatic compounds substituted on at least one of its carbon atoms by a C1-C4 alkyl group. These compounds are capable of improving the antiwear and lubricity properties of low sulfur fuel especially diesel fuels when compared with performance of the same fuel in absence of such compounds.
The use of carboxylic acid ester of an alkanolamine as an additive for improving the lubricity of low sulfur content fuel such as a diesel, bio-diesel or jet fuel has been described by Ethyl Petroleum Additives in European Patent No. EP 0773 279 A1. An interesting disclosure has been made by Placek et al in U.S. Pat. No. 5,630,852 in which lubricity of hydrocarbon fuels have been improved by the addition of a phosphorous ester or esters (phosphates and or phosphites), or a concentrate containing the ester or esters, having a total acid number of at least 1.0 mg KOH/g.
U.S. Pat. No. 6,136,050 presents invention of a diesel fuel oil composition comprising of a base fuel which contains normal paraffin compounds having carbon number of 20 or more at 4.0 wt % or less; has a specific carbon number distribution in the high boiling normal paraffin compounds contain sulfur at 0.05 wt % or less and is incorporated with 0.01 to 0.1 wt % of an friction improver and 0.002 to 0.1 wt % of lubricity improver. The lubricity improver useful for the present invention includes fatty acids and esters.
The WO 0136568, EP 1230328, JP 2003 5149537 describes the inventions related to additive mixture comprising of a) reaction product formed after reaction of a dicarboxylic acid or a derivative thereof with a long chain, aliphatic amine b) natural fatty acid ester, c) the use of said additive mixture for improving the lubricity of fuels and for improving engine resistance to wear, in addition to fuel and lubricant compositions containing said additive mixtures.
Several other patents which describe the use of additive for low sulfur diesel are WO 03/020851, WO 96/23855, WO 98/04656, FR 2772 784 Å etc.